1. Field of the Invention
The present invention relates to a client-server system including a client and a plurality of servers capable of bidirectionally sending and receiving data.
2. Description of the Related Art
A client-server system commonly includes a computer connected with various peripheral devices such as network printers and routers. Recently, the peripheral devices frequently include a built-in Web server. Such devices with a built-in Web server will be referred to as a built-in Web server for convenience sake. Japanese Patent Application Publication 10-269036 discloses a built-in Web server device.
Here, a system will be described with a personal computer and a printer connected to a network. The printer is an example of a built-in Web server device. The user can use the Web browser of the personal computer to access the Web server built into the printer in order to obtain information about the printer such as the printer status and settings of the printer. In this case, the Web browser of the personal computer displays the management setting screen (main page) shown in FIG. 1.
When the printer receives a hypertext transfer protocol (HTTP) GET request from the Web browser of the personal computer to display the management setting screen in FIG. 1, the Web server built into the printer prepares HTML (hypertext markup language) data to display the screen at the client side, and sends the data to the client. Then, the Web browser of the client receives and analyses the HTML data, and displays the main page shown in FIG. 1.
When the user clicks on hyperlinked characters or images on the main page, the built-in Web server of the printer sends the corresponding information about the printer, such as the printer's printing status and remaining amount of consumables, such as ink, toner, and paper. The information is displayed on the personal computer for the user's reference. The user can also designate various settings of the printer by clicking on the corresponding hyperlinked characters or images. In other words, the printer can be managed easily from the client side through the Web browser.
Incidentally, in the main page for performing the printer management settings shown in FIG. 1, nine types of images including a manufacturer name 71, a printer model name 72, a blue button 73, a green button 74, a red button 75, signals 76 though 78 and a printer appearance image 79 are displayed. However, when displaying each of these images, the Web browser must make an HTTP connection to the Web server for each image.
In other words, when there is the request from the Web browser to display the main page in FIG. 1, the Web server prepares HTML data and sends it to the client side. As shown in the example of FIG. 2, the HTML data does not include the data of the above-mentioned images themselves, but includes tags that indicate the source of the image files. The tags are written as <IMG SRC= . . . >. Note that the location of the image file is written as a uniform resource locator (URL).
Then, when the Web browser of the personal computer interprets the HTML data and displays the management setting screen shown in FIG. 1, each time there is an inscription such as <IMG SRC= . . . >, the Web browser makes an HTTP connection to the Web server, sends a GET request for the image file in order to download the image data from the designated URL, and then arranges the image file in place of the tag.
Therefore, when displaying the management setting screen in FIG. 1, in order to obtain HTML data and all nine image files for the main page shown in FIG. 2, the HTTP connection to the Web server is actually made 10 times, and each time the HTTP connection is made, the Web server responds to the various requests from the Web browser.
Generally, a built-in Web server device includes CPU with a smaller processing capacity than personal computers, such as those used specifically as a Web server. Therefore, when the Web browser of the personal computer sends many HTTP connection requests to the built-in Web server device, the limited capacity of the built-in Web server device's CPU may be taxed to the detriment of the built-in Web server device's main function.
In other words, when the Web browser sends many GET requests for image files, the HTTP processes performed by Web server of the built-in Web server device increase accordingly. The primary function of built-in Web server device can be adversely affected. For example, when the built-in Web server device is a printer, the printing processes can be adversely affected.
Further, as mentioned above, when there are many HTTP connection requests from the Web browser, there is also a danger of affecting the page display speed of the Web browser.
In other words, when the Web browser performs many GET requests for image files, the HTTP processes for the Web server in the integrated apparatus increases by a corresponding amount. As a result, it becomes impossible to respond quickly to GET requests from the Web browser of the personal computer.